Chronic pain is a debilitating disease affecting millions of Americans. It destroys quality of life, results in significant number of lost work days and costs billions of dollars each year. Current forms of pain management include IV and oral delivery of various opioids and other pain medication. However, both IV and oral forms of drug delivery have a number of limitations. Both, in particular oral forms, can be ineffective for the treatment of chronic breakthrough pain. Breakthrough pain is pain that comes on suddenly for short periods of time and is not alleviated by the patients' normal pain suppression management. It is common in cancer patients who commonly have a background level of pain controlled by medications, but the pain periodically “breaks through” the medication. The characteristics of breakthrough cancer pain vary from person to person
Also both oral and IV forms of opioids and other pain medication are susceptible to the development of patient addiction due to excessive self medication. Further, both put the patient at risk of overdose and underdose due to unpredictable pharmaco-kinetics. The former resulting in a number of complications including addiction, depressed respiration, irregular heart rate and even death. The latter includes continued patient exposure to chronic pain. Also, oral delivery can have poor absorption particularly in the presence of other medications or food resulting in a delayed or uneven analgesic/therapeutic effect which in turn causes the patient to take more, thus increasing the chances of addition. Also, a number of oral analgesics, NSAIDS (non-steroidal anti-inflammatory drugs) for example, cause intestinal bleeding and various GI problems, such as cramping, etc. Intravenous limitations include the requirement to mix and store the medication in liquid form as well as the use of sterile techniques in administration. Also, IV administration can include several risk factors including anaphylaxis and cardiovascular complications. Thus, there is a need for improved methods of drug delivery for pain management.
Transdermal iontophoresis is a non-invasive method of propelling high concentrations of a drug or other therapeutic agent through the skin of a human or other animal by repulsive electromotive force using a small electrical charge. The electrical charge repels ionized (i.e., charged) forms of the drug or other therapeutic agent. Using such an approach, doses of pain medication can be delivered to the patient using a skin contacting patch containing pain medication that has been dissolved in a solution disposed within the patch. The application of a current causes the dissolved medication to be propelled from the solution through a contacting layer of the patient and into the skin. However, over-administration/overdose remains a problem for such devices due to the fact that the pain medication continues to passively diffuse from the patch reservoir into the patient even when iontophoretic current is off due to concentration gradients between the patch and the skin (under the principles of Fickian diffusion). Also, there is nothing to stop the patient from overdosing themselves by reactivating the device or even leaving the current on continuously to give themselves repetitive or even continuous doses. Improved systems and methods are needed for preventing over-administration of drugs due to passive diffusion as well as excessive administration by the patient.